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Aftermarket Glock Barrel Testing

[Major Update Here]

Match Grade it Might Not Be. Or is it?

Photos by Dave Merrill and Fire-4-Effect

Scientifically determining which barrel is the most accurate is harder than you may think. No doubt the best tests are performed by engineers under lock and key at large pistol manufacturers and not found on some random internet blog or shade-tree YouTube video performed by an enthusiast. Recently, we received something different: an extensively written white paper from an accuracy test performed at the Proving Grounds of Fire-4-Effect in El Paso, Texas, to evaluate for ourselves.

In these initial tests, Fire-4-Effect sought to test just one variable: the accuracy potential of aftermarket threaded Glock 17 barrels. And indeed as stated above, this is harder to properly perform than it initially sounds. In this article, we’ll brief you on their equipment, testing procedures, and some limitations of the testing itself. As with many such controlled tests, the results ultimately raise more questions than conclusions — we view this as a positive, because it means there’s some more work to do.

Though several different brands of barrels were used in this test, given that there are a scant few (under a half dozen, to our knowledge) aftermarket Glock barrel manufacturers in the United States, there’s bound to be some overlap. With that said, we would be remiss if we didn’t mention that there can still be significant differences between barrels, even those produced at the same facility.

Firstly, many of these OEM manufacturers will build barrels to different specifications as designated by the reseller. This may be something as simple as a different coating, or as extensive as proprietary chamber dimensions. Secondly, some final fitting, machining, and coating may ultimately take place at the reseller before hitting the market, which may or may not have an effect on accuracy once that barrel is sitting in a slide.

There are seemingly endless variables that all have an effect on repeatable accuracy. When shooting a handgun at the range, accuracy is determined by a combination of ammunition, all aspects of the firearm such as lockup and how the barrel is constricted by the slide, and the shooter — with the shooter bringing the greatest amount of variability to the table. The shooter is the biggest wildcard by a very large margin.

The Barrels
Fire-4-Effect bought 15 barrels off the shelf from eight different identifying brands; the plan was to have at least two barrels from each brand to help reduce any outliers. They purchased the barrels “blind” from assorted distributors without disclosing their intentions. This was to ensure they would receive a “typical” barrel just like any other customer. Though each barrel is threaded, no silencers or other muzzle devices were used during the testing itself.

The barrels tested.

The barrel is secured in the rear of the fixture, and the front tensioning knob is to simulate it being inside a slide.

If you’ve done the math, you’ll quickly realize that it doesn’t add up; this is because only one OEM threaded Glock barrel could be obtained for this test. For this reason, we excluded the performance of the factory threaded Glock barrel from the results.


The Ammunition
For ammunition Fire-4-Effect selected three different types to test in each barrel:

Control: Atlanta Arms 115-grain FMJ Match AMU (all from the same lot, 629165)
Defensive: Federal 147-grain JHP (manufacturer SKU 9MS)
Practice: Remington UMC 115-grain FMJ

Taking the Man and the Gun out of the Equation
In order to isolate the test to the barrel itself, Fire-4-Effect designed and manufactured a custom firing fixture. It’s based on a design used by the Army Marksmanship Unit (AMU), no surprise given the senior gunsmith at Fire-4-Effect is Matt Haidu, a recently retired Army soldier who spent more than a decade in the AMU custom shop building and using fixtures like this one.

The testing base itself weighs more than 10 pounds. In order to reduce environmental vibrations, the crew at Fire-4-Effect bolted the entire device to a solid platform with ¾-inch bolts, rooting the legs of the platform several feet into a concrete foundation. While an earthquake or a fleet of Abrams driving by could introduce stray tremors, not much more could.

The open-firing mechanism can be seen on the right- hand side of this photo.

The fixture partially disassembled.

Not only is the human element eliminated from the equation, but so was particular barrel/slide fitment. The fixture also sports an adjustable support intended to mimic the interference between the slide and the barrel. The test was performed indoors in a climate-controlled environment to eliminate variations in temperature or humidity.

“Our fixture gives the barrel every opportunity to perform at its very best with minimal outside influence,” William Wingfield of Fire-4-Effect explained.

The least fun part of any real test: data input and collation.

Testing Procedure
The target for each test was set at 20 yards. Each barrel was placed and secured into the test fixture. A single “spotter round” was fired using the Remington UMC 115-grain ammunition to determine the rough point-of-impact area, and a fresh target was placed there.

Next a string of 10 rounds of the control ammunition (Atlanta Arms 115-grain FMJ Match AMU) was fired. If the shot group of the control ammunition was considered too large or seemed characteristic of improper barrel mounting, the barrel was removed and remounted into the fixture according to procedure and a control group was fired again.

If the barrel passed the grouping test with the control ammunition, the same shot sequences were performed with both the defensive (Federal 147-grain JHP) and practice (Remington UMC 115-grain FMJ).

Every round fired was chronographed and logged, and every group was measured for horizontal, vertical, and extreme spread using a Mitutoyo dial caliper.

Chronograph Results
It shouldn’t be a surprise that none of the ammunition supplied had exactly matching advertised and measured speeds, though they were similar. While variations in velocity can be observed within the same lot or even in the same box of ammunition, Fire-4-Effect found the barrels themselves to be the largest determining factor. They theorize chamber size, throat depths, and internal finishes make large contributions to the final velocity of each round tested. However, variability in velocity appeared to have little or no relationship to the accuracy of a given barrel when fired from the testing fixture.

Before delving into the actual results of this test, we should discuss its limitations. When we asked Wingfield of Fire-4-Effect, the very first thing he pointed out was the extremely small sample size. While two barrels from each named brand is certainly better than one, increasing that number would provide more statistically significant results. The same goes for the types and number of rounds fired. Put another way, the results of this test would hold significantly more statistical weight if larger sample sizes were tested.

RECOIL reached out to a number of unaffiliated subject-matter experts on accuracy testing and asked them to evaluate both the test and the fixture itself. Mark Hammond, VP of project engineering at Atlas Development Group, is an engineer who has been in firearms development since 2004, with nine of those years spent performing R&D for Remington. He had this to say:
“If you’re testing intrinsic accuracy of the barrel itself, what they’re doing does seem like a good way to isolate out exterior geometry. But as for exactly how it’s going to perform in the gun there are several other variables that contribute to accuracy.”

Hammond further stated, “What’s open to debate in my mind is what percentage of exterior dimensions affect accuracy since there is some slide movement [when fired] before the bullet exits. From an engineering perspective I would use a test like this to determine a desired type of rifling, but if I were really testing accuracy I would move toward testing the barrels in full-on firearms.”

Ethan Lessard, current VP of engineering at Q, longtime engineer with SIG SAUER, and former head of engineering at AAC, also had some input on the testing and fixture.

With a MagnetoSpeed chronographed installed, the test fixture would look right at home at a steampunk convention.

The indoor range at Fire-4-Effect’s Proving Grounds.

“The thing you care about is how the barrel changes accuracy in any way [relative to an OEM barrel]. If you want to find that out, you have to actually put it [the aftermarket barrel] in the gun.”

“Without seeing it disassembled and knowing exactly what knobs are turned down, I would say it looks far overconstrained. I can tell you for sure the barrel is not being constrained the same way that it would be in the gun.”
Lessard continued, “Your best shooting barrel out of this fixture could be your worst shooting barrel out of the gun. The way a pistol barrel is constrained in the gun when your gun is in battery is one thing; upon firing, when the bullet makes the jump to the rifling, the barrel, and slide will begin to move before the bullet exits … I’ve found that changing things on the outside of the barrel affected accuracy and precision far more than what was on the inside of the barrel, provided concentricity of the chamber and bore is consistent.”

Because there’s some contention regarding the sample size and methodology of this particular test, RECOIL didn’t feel it prudent to list the individual brand names alongside the results. However, even if you do, take note that on face value even the worst performing barrel with the most inconsistent ammunition in this test will outperform most shooters at 20 yards.

Red: best group at 20 yards. Yellow: worst group at 20 yards.

[Red: best group at 20 yards. Yellow: worst group at 20 yards.]

This has not, however, stopped Fire- 4-Effect from developing a new testing protocol, to account for the actual barrel/slide treatment and its overall effect on accuracy. They’ll share these results with us, and we’ll share them with you on March 23, the day that this issue hits the shelves. We’ll also be publishing the full, non-redacted white paper that inspired this article along with it on

We look forward to seeing the results of the new set of tests, and if they match up with the accuracy results born from this testing fixture. Remember: Real testing is long, boring, expensive, and makes for a terrible YouTube video. Stay tuned.



[The Latest Test Results are live here at this link–this new data has made us comfortable with releasing the names of each test barrel. Remember to read both parts and keep everything in the proper context]



Blacklist, Barrel 1 671.51 1.05
Blacklist, Barrel 2 174.54 0.87
KKM, Barrel 1 356.54 0.73
KKM, Barrel 2 256.06 0.99
Lone Wolf, Barrel 1 410.40 1.13
Lone Wolf, Barrel 2 305.88 1.49
S3F, Barrel 1 158.46 0.72
S3F, Barrel 2 168.01 0.96
SilencerCo, Barrel 1 298.32 0.85
SilencerCo, Barrel 2 333.79 0.68
Storm Lake, Barrel 1 264.54 0.92
Storm Lake, Barrel 2 384.68 0.82
ZEV, Barrel 1 670.84 1.21
ZEV, Barrel 2 806.68 1.38


VERT SPREAD 0.785 0.600 1.490
HORIZ SPREAD 1.175 1.080 2.050
EXTREME SPREAD 1.175 1.080 2.050
CUMULATIVE AVG 1.045 0.920 1.863
VERT SPREAD 0.930 0.978 1.565
HORIZ SPREAD 0.740 0.740 2.751
EXTREME SPREAD 0.930 1.170 2.751
CUMULATIVE AVG 0.867 0.963 2.356
VERT SPREAD 0.715 0.770 1.510
HORIZ SPREAD 0.580 0.870 1.375
EXTREME SPREAD 0.908 0.900 1.790
CUMULATIVE AVG 0.734 0.847 1.558
VERT SPREAD 0.910 1.080 1.920
HORIZ SPREAD 0.950 1.585 1.110
EXTREME SPREAD 1.103 1.763 2.203
CUMULATIVE AVG 0.988 1.476 1.744
VERT SPREAD 0.690 0.665 1.630
HORIZ SPREAD 1.260 0.740 1.680
EXTREME SPREAD 1.430 0.740 1.975
CUMULATIVE AVG 1.127 0.715 1.762
VERT SPREAD 1.610 0.750 1.455
HORIZ SPREAD 1.214 0.745 1.890
EXTREME SPREAD 1.650 0.810 2.020
CUMULATIVE AVG 1.491 0.768 1.788
VERT SPREAD 0.675 0.860 1.260
HORIZ SPREAD 0.680 0.790 1.030
EXTREME SPREAD 0.790 0.860 1.465
CUMULATIVE AVG 0.715 0.837 1.252
VERT SPREAD 0.625 1.230 1.062
HORIZ SPREAD 1.120 0.815 1.092
EXTREME SPREAD 1.120 1.420 1.270
CUMULATIVE AVG 0.955 1.155 1.141
VERT SPREAD 0.670 1.130 0.130
HORIZ SPREAD 0.890 0.608 1.080
EXTREME SPREAD 0.983 1.151 1.250
CUMULATIVE AVG 0.848 0.963 0.820
VERT SPREAD 0.580 0.515 1.470
HORIZ SPREAD 0.630 0.760 0.688
EXTREME SPREAD 0.840 0.765 1.470
CUMULATIVE AVG 0.683 0.680 1.209
VERT SPREAD 0.780 0.580 0.750
HORIZ SPREAD 0.930 0.826 1.021
EXTREME SPREAD 1.060 0.919 1.081
CUMULATIVE AVG 0.923 0.775 0.951
VERT SPREAD 0.885 0.650 1.693
HORIZ SPREAD 0.570 0.920 1.820
EXTREME SPREAD 0.990 0.935 2.180
CUMULATIVE AVG 0.815 0.835 1.898
VERT SPREAD 1.335 1.135 1.640
HORIZ SPREAD 0.866 0.960 1.760
EXTREME SPREAD 1.420 1.408 2.220
CUMULATIVE AVG 1.207 1.168 1.873
VERT SPREAD 1.040 0.740 1.370
HORIZ SPREAD 1.490 0.850 1.963
EXTREME SPREAD 1.610 1.020 2.070
CUMULATIVE AVG 1.380 0.870 1.801



For complete data sets, visit Fire-4-Effect online here. And don’t forget to check out Part 2 of the testing here.

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